Machine for forming piston ring spacer-expanders from strip stock

ABSTRACT

A machine for making spacer-expanders for piston oil rings of the type described in U.S. Pat. No. 3,477,732. The machine comprises a punch press having a plurality of stations through which strip stock is fed progressively in accurately predetermined increments, the strip stock being worked between dies at each station to transform the strip stock into completed rings. The press includes one or more punching stations where the strip stock is pierced and blanked, one or more forming stations where the pierced and notched strip is bent to form the spring legs of the spacer-expander and then curled into a channel-shaped cross-section, a coiling station where the channel-shaped stock is fashioned into a coil, and a cut-off station where each coil is sheared from the strip to form the semi-finished ring. The press also includes a special transfer apparatus for transferring the semi-finished ring to a final work station wherein the end joints are trimmed and formed to final configuration, after which the finished rings are loaded automatically in stacked relation on a cylindrical mandril.

United States Patent 1 Overway MACHINE FOR FORMING PISTON RING SPACER-EXPANDERS FROM STRIP STOCK [75] Inventor: Roy E. Overway, Grand l-laven,

Mich.

[73] Assignee: Sealed Power Corporation,

Muskegon, Mich.

[22] Filed: Nov. 5, 9171 [21] Appl. No.: 196,240

Related 0.8. Application Data [62] Division of Ser. No. 39,498, May'21, 1970, Pat. No.

Primary ExaminerCharles W. Lanham Assistant Examiner-Robert M. Rogers Attorney-Barnes, Kisselle, Raisch & Choate Oct. 23, 1973 [57] ABSTRACT A machine for making spacer-expanders for piston oil rings of the type described in US Pat. No. 3,477,732. The machine comprises a punch press having a plurality of stations through whichstrip stock is fed progressively in accurately predetermined increments, the strip stock being worked between dies at each station to transform the strip stock into completed rings. The press includes one or more punching stations where the strip stock is pierced and blanked, one or more forming stations where the pierced and notched strip is bent to form the spring legs of the spacer-expander and then curled into a channel-shaped cross-section, a coiling station where the channel-shaped stock is fashioned into a coil, and a cut-off station where each coil is sheared from the strip to form the semi-finished ring. The press also includes a special transfer apparatus for transferring the semi-finished ring to a final work station wherein the end joints are trimmed and formed to final configuration, after which the finished rings are loaded automatically in stacked relation on a cylindrical mandril.

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o5 ovm wmm mmw ow- PAIENIEUmn 23 km SHEET 15 0F 17' PNm - m max H E 6 K H 7 w. M -EIIL v lmilll MACHINE FOR FORMING PISTON RING SPACER-EXPANDERS FROM STRIP STOCK tallic rails in the oil groove of a piston of an internal combustion engine.

An object of this invention is to enable production of such rings accurately, economically and at a high rate.

Another object is to provide an improved machine capable of automatically forming spacer-expanders of the type disclosed in US. Pat, No. 3,477,732, particularly in connection with FIGS. 1-5 inclusive and FIGS. 15 and 16 thereof. a

A further object is to provide an improved machine capable of performing the improved method of making such a spacer-expander as disclosed in a co-pending application of Frank G. Warrick, Ser. No. 448,059, filed Apr. 14, 1965, now U.S. Pat. No. 3,477,732 entitled Method of Forming a Spacer-Expander, and assigned to the assignee of the present application.

A further object is to provide an improved machine of the above character utilizing certain components and functions ofthe machine disclosed and claimed in- U.S. Pat. No. 2,925,847, assigned to the assignee of the present application, and to improve upon said prior machine. I

I Other objects,'features and advantages of the apparatus of this invention will become apparent from the following detailed description and accompanying drawingswherein:

FIG. 1 is a fragmentary front elevational view of an exemplary but preferred embodiment of the machine of the present invention. n I

FIGS. 2, 3 and 4- are "fragmentary plan views of the strip stock respectively showing the operations performed thereon at the first, second and third punching, blanking and bending stations of the machine.

FIG. 5 is a fragmentary perspectiveview of the strip stock illustrating the feet and leg bending operations performed thereon successively at stations Nos. 3 and 4 respectively. 7 I

' FIG. 6 isa fragmentary view partially in vertical elevation and partially in vertical center section through the strip guide in'feeding-mechanism and leg bending dies of station No. 4. FIGS. 7 and 8 are fragmentary end elevational and part vertical sectional views taken generally on the line 7-7 of FIG. 6 and'respectively illustrating the dies of station No.4 in their open and closed positions.

FIG. 9 is a fragmentary plan view of the strip infeed guide of station No. 4. i

FIGS. 10 and 11 are fragmentary enlarged views of the dies as viewed in FIGS. 7 and 8 respectively.

FIG. 12 is a fragmentary front elevational view showing a portion of the die structure shown in FIG. 6 but enlarged thereover and with the dies in closed position.

FIG. 13 is a vertical sectional view taken on the line 13-13 of FIG. 5 but enlarged thereover.

FIG. 14 is a fragmentary front elevational view of the dies of station No. 5 shown partially in vertical center section and with the dies closed.

FIG. 15 is a fragmentary end elevational view of the I entrance to station No. 5 taken on the line 15-15 of FIG. 14.

FIG. 16 is a fragmentary vertical sectional view taken on the line 16-16 of FIG. 21 and illustrating the progressive strut bending operation being simultaneously performed by the last even of the ten punches and associated dies of station No. 5.

FIGS. 17, 18, 19, 20 and 21 are fragmentary vertical sectional views taken respectively on the line 17-17 of FIG. 14 and lines 18-18, 19-19, 20-20 and 21-21 of FIG. 16.

FIG. 22 is a vertical sectional view taken on the line 22-22 of FIG. 16 illustrating the finished crosssectional contour of the strip as it emerges from station FIG. 23 is a fragmentary horizontal sectional view taken on the line 23-23 of FIG. 14 illustrating the stationary stripper components in the lower die shoe of station No. 5. 7 FIG. 24 is a fragmentary horizontal plan view of a portion of the structure shown in FIG. 23 with thestationary stripper parts removed to better illustrate the underlying movable stripper and stationary forming dies' in the lower die shoe. 7

FIGS. '25, 26 and 27v are fragmentary vertical sectional views taken respectively on the lines 25-25, 26-26 and '27-27 of FIG. 14.

FIG. 28 is a fragmentary perspective view of the left- I hand stripper plate of station No. 5 shown by itself.

FIG. 29 is a fragmentary front elevational view of a portion of the induction heating coil of station No; 6 and also illustrating the coiling and cut-off apparatus of station No. 7 of the machine. I

FIG. 30 is a fragmentary front elevational view of the components of station No. 7 with the guide shield and blow-off air tube parts removed to better'illustrate details.

FIG. 31 is afragmentary end elevational view of the entrance guide of station No. 7 looking in the direction FIG. 33 is a fragmentary vertical sectional view taken on the line 33-33-of FIG. 30. FIG.-34 isa fragmentary plan view of the strip stock after it has beensevered in the cut off operation of station No. 7. i

FIG. 35 is a fragmentary front elevational view ofa portion of station- No. .7 illustrating the strip coiling anvil and associated bending pad in the open position thereof. r 6

FIG. 36 is a fragmentary end elevational view of actuating linkage in station No. 7 as viewed on the line 36-36 of FIG.30. v FIG. 37 is a fragmentary front elevational view of the apparatus of stations Nos. 8 and 9 of the machine.

FIG. 38 is a fragmentary front elevational view of a portion of the station No. 8 apparatus shown in FIG. 37 but illustrating the pusher members in closed position embracing the entrance cone of this station.

FIG. 39 is a side elevational view of the apparatus of station Nos. 8 and 9 FIG. 40 is a fragmentary horizontal sectional view taken on the line 4040 of FIG. 37 illustrating a portion of the apparatus of station No. 9.

FIG. 41 is a horizontal sectional view taken on the line 4141 of FIG. 37.

FIG. 42 is a horizontal sectional view taken on the line 4242 of FIG. 37.

FIG. 43 is a fragmentary horizontal section of the shot pin and slide parts of FIG. 42 but with the shot pin shown in engaged position with the slide.

FIG. 44 is a fragmentary side elevational view illustrating the punch, clamp and die components of station No. 8, FIG. 44 being partially taken in vertical center section and enlarged over FIG. 39.

FIG. 45 is a fragmentary vertical sectional view taken on the line 45-45 of FIG. 44.

FIG. 46 is a fragmentary horizontal sectional view taken on the line 46-46 of FIG. 44 but greatly enlarged thereover.

FIG. 47.is a fragmentary vertical sectional view taken on the line 4747 of FIG. 46.

FIG. 48is'a fragmentary plan view of a portion of the parts shown in FIG. 46 but with their position changed to illustrate the joint trimming and initial bending action.

FIG. 49 is a view similar to FIG. 48 showing the parts at the completion of the trim and bending stroke.

FIG. 50 is a fragmentary side elevational view of the left-hand clamp member shown in FIGS. 46, 48 and 49.

FIG. 51 is'a fragmentary side elevational view of the right-hand shearing and bending punch shown in FIGS. 46, 48 and 49.

FIG. 52 is an end elevational view of the left-hand forming'die shown in FIGS. 46, 48 and 49.

FIG. 53 is a fragmentary perspective view of one end of the spacer-expander illustrating the end joints thereof after being trimmed and bent in station No. 8.

For purposes of facilitating description and not by way of limitation, the machine 100 of the present invention is illustrated with the proper dies for forming the piston ring spacer-expander illustrated in the aforementioned United States Warrick U.S. Pat. No. 3,477,732, particularly the spacer-expander 58 shown and described in conjunction with FIGS. 1-5 inclusive thereof and with the end joint construction shown and described in conjunction with FIGS. 14-16 inclusive thereof, this patent being incorporated herein by reference and hence spacer-expander 58 thereof not being described herein.

GENERAL ARRANGEMENT 7 Machine 100 of the present invention is shown substantially in its entirety in FIG. 1 and generally consists of a punch press similar in part to that shown, described and claimed in the aforementioned U.S. Bums et al. U.S. Pat. No. 2,925,847, which is incorporated herein by reference for a detailed disclosure of certain portions of the machine identified in more detail hereinafter. Machine 100 has a base 102 which supports a frame 104 and a motor 106 on frame 104 which drives a flywheel 108 through a belt 110. Flywheel 108 is connected by a clutch 112 with the crankshaft 114 of the press. Clutch 112 is of the positive drive, electric throw-out type. Shaft 114 is journalled on the frame of the machine in bearings 116. A pair of magnetic brakes 118 are arranged around shaft 114 and when electrically energized operate to sieze shaft 114when the circuit to the brake is opened. Shaft 114 has three crank portions to which the upper ends of connecting rods 120, 122 and 124 are individually pivotally connected. Rods 120, 122, and 124 are connected respectively at their lower ends to associated rams 126, 128 and 130 which are guided for vertical reciprocating movement on frame 104 in ways formed in three sets of guide plates 132, 133 and 134 respectively.

As set forth in more detail hereinafter, ram 126 operates a piercing die assembly 136 of station N0. 1 and a blanking and notching die assembly 138 of the station No. 2. Ram 128 operates a foot bending and joint notching die assembly 140 of station No. 3 and a leg bending die assembly 142 of station No. 4. Ram 130 operates a strut bending and strip curling die assembly 144 of station No. 5 and, also, through a linkage 804, operates a coiling and cut-off die assembly 146 of station No. 7. The end joint trimming and bending die assembly 148 of station No. 8 is powered by pneumatic rams synchronized with the operation of the press by a suitable counting and control mechanism as described in more detail hereinafter.

The end of shaft 114 remote from flywheel 108 carries a disc 150 to which a link 152 is eccentrically connected for driving a strip feeder 154 through a bell crank 156. A suitable commercially available magnetic pick-up assembly is provided for counting revolutions of shaft 114 to develop one signal per each vertical reciprocation of the rams 126, 128 and 130 through their simultaneous mechanically synchronized working strokes. Pick-up 160 has a rotating part 162 secured to shaft 114 for rotation therewith and a stationary part 164 secured to the stationary structure of the end bearing 1 16. Pickup 160 provides the input signal to a suitable counter control (not shown), such as that sold under the trademark DYNAPAR made by the Louis Allis Division of LItton Industries at the Digital Center in Gurnee, Illinois and identified as a Digital Process Controller Type 5X2-58-X-1. This controller operates through the signals derived from pick-up 160 to initiate the cut-off operation as well as the air blast at station No. 7. This occurs in response to an outputsignal developed by storing the number of counts in the digital memory of the controller corresponding to the number of increments of advance of the strip being worked in machine 100 required to pass a given length spacerexpander through the coiling die of station No. 7. Also,

this control further provides an output signal for actuating the pusher fingers of station No. 8 after allowing a time delay (corresponding to a given number of counts) for the severed spacer-expander to vc lrop onto the nose cone of station No. 8. The remaining motions in stations Nos. 8 and 9 are controlled by conventional limitswitches and solenoid valve circuitry (not shown) associated with the moving parts of this station as described in more detail hereinafter. 1

The counter control is also adapted to generate a 1 control signal for causing a transverse shuttle motion of die assemblies 136, 138 and 140 of stations Nos. 1, 2 and 3 as an end joint zone of the strip stock being fed therethrough comes into successive registry with the respective die assemblies, as set forth in more detail hereinafter.

In general, the operation of machine 100 is as follows: 

1. Apparatus for forming strip stock into rings comprising a coiling die assembly, means for feeding strip stock of generally channel-shaped cross-section with a step-by-step movement through said coiling die assembly, said coiling die assembly being located in the path of travel of the strip downstream from said feeding means and having a punch movable toward and away from the channel-shaped strip and an anvil disposed adjacent the side of said strip opposite said punch, said punch having a forming surface adapted to impart a coiling curvature to the strip in angular increments circumferentially of the strip to thereby progressively coil the strip into a ring, said anvil having a forming surface complementary to said forming surface of said punch, said punch being mounted for pivotal movement about an axis parallel to the axis of a ring being formed by said coiling die assembly such that said punch forming surface is movable toward and away from said anvil forming surface with the strip disposed between said forming surfaces to curve successive increments of the strip to thereby form a generally circularly shaped ring, and drive means for pivotally moving said punch to opened and closed positions of said coiling die assembly in synchronism with said strip feeding means to thereby advance the strip stock when said coiling die assembly is open and to hold the strip stock stationary during closing movement of said coiling die assembly.
 2. The combination as set forth in claim 1 wherein said punch is operable against the side of said strip which becomes the oUter periphery of the ring.
 3. The combination as set forth in claim 1 wherein said axis about which said punch is mounted for pivotal movement is upstream of said forming surface of said punch relative to the direction of strip feed.
 4. The combination as set forth in claim 1 wherein said drive means comprises a ram reciprocable in the direction of the opening and closing movement of said coiling die assembly, and an articulated linkage mechanically coupling said drive means to said coiling die punch and operable in response to closing movement of said ram to move said punch in a direction generally opposite to the direction of said closing movement of said ram, and vice versa.
 5. The combination as set forth in claim 4 wherein said linkage has a lost-motion connection between said punch and said ram operable to cause said ram to impart closing movement to said punch during travel of said ram only in the last portion of said ram''s closing movement, means biasing said punch to its open position during all but said last portion of the closing travel and the corresponding successive initial opening travel of said ram, and wherein said strip feeding means is operable to feed said strip when said coiling punch is open.
 6. The combination as set forth in claim 5 wherein said linkage comprises a rigid arm secured to said ram and extending to said coiling die assembly and having a follower dependent therefrom, a first lever pivoted for movement in a plane aligned with the path of travel of said arm follower, a rock shaft mounted for rotation about the longitudinal axis of said shaft and oriented with said axis perpendicular to said plane, a second lever secured to one end of said shaft and extending radially therefrom in converging relation with said first lever, said second lever having a follower tracking on the side of said first lever opposite said arm follower, said coiling punch being secured to said rock shaft and extending radially therefrom generally in the opposite direction from said second lever, said arm follower contacting said first lever between its pivot point and said second lever follower during said last portion of the closing movement of said ram to thereby swing said coiling punch in a closing stroke in a direction opposite to the direction of travel of said arm follower.
 7. The combination as set forth in claim 1 further including a cut-off punch and die assembly positioned between said feeding means and said coiling die assembly, said cut-off punch and die assembly having a punch reciprocable across the path of travel of said strip to sever the uncoiled portion of the strip from the leading coiled portion of the strip, and means for operating said cut-off punch member through its working stroke at regular intervals corresponding to a given number of coiling punch strokes.
 8. The combination as set forth in claim 7 wherein said cut-off punch and die assembly comprises a stationary cut-off die having an end surface facing said cut-off punch and extending in the direction of strip feed from upstream of said cut-off punch to at least the entrance ends of said coiling punch and anvil, and a guideway for feeding said channel-shaped strip onto said end surface of said cut-off die with said strip oriented with its median portion sliding along said end surface and its side margins bearing against said anvil forming surface.
 9. The combination as set forth in claim 8 wherein said cut-off die has a narrow trailing rib disposed opposite said coiling anvil and aligned with the strip median, and wherein said coiling punch has a slot in its entrance end receiving said rib therein, said rib having an end surface forming an extension of said cut-off die end surface and being generally flush with said coiling punch surface in the closed position thereof.
 10. The combination as set forth in claim 7 wherein said cut-off punch operating means comprises a movable linkage coupled between said ram and coiling die assembly drive means, said linkage having a part movable in a direction of motion parallel to that of the working stroke of said cut-off punch, and a shuttle part carried on said linkage part for movement therewith, said shuttle part also being movable in a direction perpendicular to said travel of said cut-off punch between positions engaging and clearing said cut-off punch to thereby respectively connect and disconnect said linkage in driving relation with said cut-off punch, and means for moving said shuttle part to its engaging position at said regular intervals to transfer one stroke of said ram to said cut-off punch.
 11. The combination as set forth in claim 10 wherein said anvil is disposed above said strip and said coiling punch is disposed below said strip, said forming surfaces of said coiling punch and anvil curving upwardly whereby said strip is coiled upwardly by striking the outer periphery thereof to position the fully coiled ring above said coiling punch.
 12. The combination as set forth in claim 6 further comprising a cutoff punch and die assembly positioned between said feeding means and said coiling die assembly, said cut-off punch and die assembly having a punch reciprocable across the path of travel of said strip to sever the uncoiled portion of the strip from the leading portion of the strip, a movable linkage coupled between said ram and said drive means of said coiling die assembly, a part mounted on said rigid arm of said linkage and movable in a direction of motion generally parallel to that of the working stroke of said cut-off punch, and a shuttle part carried on said part mounted on said rigid arm for movement therewith, said shuttle part also being movable in a direction generally perpendicular to said travel of said cut-off punch between positions engaging and clearing said cut-off punch to thereby respectively connect and disconnect said linkage in driving relation with said cut-off punch, and means for moving said shuttle part to its engaging position at regular intervals to transfer one stroke of said ram to said cut-off punch.
 13. The combination as set forth in claim 7 wherein said coiling die assembly has a guide plate mounted adjacent the path of travel of said strip as it curls up into a coil upon leaving said coiling punch and anvil, and means for directing an air blast adjacent said guide plate directed toward said coiled strip in response to said strip being severed by said cut-off punch to thereby eject the severed coiled ring endwise in a direction transverse to strip feed.
 14. The combination as set forth in claim 13 wherein said air blast means comprises a semi-circular tube positioned adjacent but radially outwardly of the position of a fully coiled ring and adjacent said plate, said tube having nozzle means circumferentially spaced along the inner periphery of said tube for directing a plurality of air jets radially inwardly toward said ring and generally parallel to said plate.
 15. The combination as set forth in claim 13 wherein said guide plate has an entrance portion adjacent the exit ends of said coiling punch and anvil and inclined from the plane of said guide and diverging outwardly from the path of travel of said strip to feed the severed leading end of the strip onto the guiding surface of said plate.
 16. The combination as set forth in claim 13 further including a stringer tube adapted to receive said severed ring thereon, said tube having an entrance nose positioned generally within the area bounded by said ring when said ring is positioned adjacent said plate in its substantially completely coiled form.
 17. The combination as set forth in claim 16 wherein said stringer tube has a cylindrical portion smaller in diameter than that of the completely coiled ring but sufficiently large to prevent the gaps of said ring from passing transversely thereover, and said tube has a ring orienting fin extending radially outwardly from said tube and running lengthwise thereof, said fin being generally aligned with said cut-off punch and die assembly So that the parted ends of said ring as it is being severed from said strip are disposed on opposite sides of said fin.
 18. The combination as set forth in claim 17 wherein said guide plate has an apron inclined downwardly and outwardly therefrom disposed over the path of travel of said strip leading onto said cut-off die assembly, said apron being positioned to slidably divert the leading end of the coiled strip outwardly toward said stringer tube preparatory to severance of said coiled strip and transfer of the severed ring to said stringer tube.
 19. The combination as set forth in claim 18 wherein said fin has a flange extending transversely from the longitudinal edge of said fin remote from said stringer tube, said apron extending at its trailing end adjacent to said fin and above said flange.
 20. The combination as set forth in claim 6 further including a forming die assembly located in the path of strip feed between said feeding means and said coiling die assembly, said feeding means feeding said strip stock in generally flat form with a step-by-step movement through said forming die assembly, said forming die assembly being adapted to form successive increments of said strip into a generally channel-shaped cross-section, said ram having a direct one-to-one connection to said forming die assembly and being reciprocable upwardly and downwardly to impart opening and closing movement respectively to said forming die assembly and coiling die assembly to operate said forming and coiling die assemblies in synchronism but in opposite directions.
 21. Apparatus for forming strip stock into rings comprising a coiling die assembly, means for feeding strip stock of generally channel-shaped cross-section with a step-by-step movement through said coiling die assembly, said coiling die assembly being adapted to curve successive increments of said strip to thereby form a generally circularly shaped ring, said coiling die assembly being located in the path of travel of the strip downstream from said feeding means and having a punch movable toward and away from the channel-shaped strip, said punch having a forming surface adapted to impart a coiling curvature to the strip in angular increments circumferentially of the strip to thereby progressively coil the strip into a ring, said coiling die assembly also having a stationary anvil disposed adjacent the side of said strip opposite said punch and having a forming surface complementary to said forming surface of said punch, drive means for opening and closing said punch in synchronism with said strip feeding means to thereby advance said strip when said coiling die assembly is open and to hold said strip stationary during closing movement of said coiling die assembly, a cut-off punch and die assembly positioned between said feeding means and said coiling die assembly, said cut-off punch and die assembly having a punch reciprocable across the path of travel of said strip to sever the uncoiled portion of the strip from the leading coiled portion of the strip and a stationary cut-off die having an end surface facing said cut-off punch and extending in the direction of strip feed from upstream of said cut-off punch to at least the entrance ends of said coiling punch and anvil, means for operating said cut-off punch through its working stroke at regular intervals corresponding to a given number of coiling punch strokes, and a guideway for feeding said channel-shaped strip onto said end surface of said cut-off die with said strip oriented with its medium portion sliding along said end surface and its side margins bearing against said anvil forming surface.
 22. The combination as set forth in claim 21 wherein said cut-off die has a narrow trailing rib disposed opposite said coiling anvil and aligned with the strip median, and wherein said coiling punch has a slot in its entrance end receiving said rib therein, said rib having an end surface forming an extension of said cut-off die end surface and being generally flush with said coiling punch surface in the closing position thereof.
 23. The combination as set forth in claim 21 wherein said cut-off punch operating means comprises a movable linkage coupled between said ram and coiling die assembly drive means, said linkage having a part movable in a direction of motion parallel to that of the working stroke of said cut-off punch, and a shuttle part carried on said linkage part for movement therewith, said shuttle part also being movable in a direction perpendicular to said travel of said cut-off punch between positions engaging and clearing said cut-off punch to thereby respectively connect and disconnect said linkage in driving relation with said cut-off punch, and means for moving said shuttle part to its engaging position at said regular intervals to transfer one stroke of said ram to said cut-off punch.
 24. The combination as set forth in claim 23 wherein said anvil is disposed above said strip and said coiling punch is disposed below said strip, said forming surfaces of said coiling punch and anvil curving upwardly whereby said strip is coiled upwardly by striking the outer periphery thereof to position the fully coiled ring above said coiling punch.
 25. Apparatus for forming rings from strip stock having a sufficient continuous axial length to permit multiple rings to be formed therefrom comprising a coiling die assembly, means for feeding strip stock with a step-by-step movement through said coiling die assembly, said coiling die assembly being located in the path of travel of the strip downstream from said feeding means and having a punch movable toward and away from the strip stock and a stationary anvil having a curved forming surface disposed adjacent the side of the strip stock opposite said punch for imparting a coiling curvature to a segment of the strip stock in angular increments circumferentially of the strip stock to thereby progressively coil a portion of the strip stock into a ring, a guide for aligning and retaining an axially extending portion of the strip stock upstream of said punch generally tangential to a point on the curved forming surface of said anvil, said punch having a forming surface complementary with said curved forming surface of said anvil, said punch forming surface extending only generally downstream of said point such that said die assembly imparts a coiling curvature to the strip stock only generally downstream of said point, said guide bearing on a side of the strip stock remote from the anvil and upstream of said point to thereby retain said axially extending portion of the strip stock upstream of said punch generally tangential to said point while said coiling die assembly imparts a coiling curvature to a portion of the strip stock downstream of said point, and drive means for moving said punch to opened and closed positions of said coiling die assembly in synchronism with said strip feeding means to thereby advance the strip stock when said coiling die assembly is open and to hold the strip stock stationary during closing movement of said coiling die assembly.
 26. The combination as set forth in claim 25 wherein said forming surface of said punch is mounted for pivotal movement about an axis upstream of said forming surface of said punch relative to the direction of strip feed and parallel to the axis of a ring being formed by said coiling die assembly.
 27. The combination as set forth in claim 26 wherein said anvil is disposed above said strip and said punch is disposed below said strip with said forming surfaces of said punch and anvil curving upwardly whereby said strip is coiled upwardly by said coiling die assembly to position the fully coiled ring above said punch. 